ggcorr -- draw a correlation plot matrix with ggplot2

Inspired by a Stack Overflow question
<http://stackoverflow.com/q/12196756/635806>. Would be very happy to
improve the code.
erge branch 'master' of github.com:briatte/ggally into briatte-master
removed first plot to speed up testing / pass checks
documented
added ggcorr from Francois Briatte.  Added '...' to feed into geom_text.  (had to remove the default of size = 4)
updated description and released
ggnet submission -- a function for making a network plot from an object of class network or igraph, using ggplot2

https://github.com/briatte/ggnet
typo
typo
precision in example
example correction
gitignore
additional city-firms example
robust node.group argument
network package dependency
better example code
example correction
additional functions

functions used in a paper using website networks
little improvements

labels not drawn if all missing; function robust to igraph/network
namespace conflict
robust call to sna